- Non response and lost-to-follow up 30% Using SATA clustersampsi command, sample size per study arm is calculated as 175 children of 18-24 months age. 7 children in each of 25 clusters (~2000 population each) would be followed up from ~125 days of gestational age to postnatal 24 months. The sample size in comparison arm will be doubled for analysing some secondary indicators.